Glycosphingolipids (GSLs) are cell surface components that have intrinsic interest as antigens and receptors, and they are also useful for analysis of cell membrane organization and differentiation. This project includes studies of human lymphocyte GSLs and of the human blood group P system. Lymphocyte glycolipids - We have found that at least three subpopulations of human B lymphocytes can be identified by their immunofluorescent reactions with antibodies to six GSLs: lactosylceramide, trihexosylceramide, globoside, papragloboside, GM1 and asialo GMI. Approximately 25% of normal B cells are unreactive with all six antibodies, as are B lymphocytes from 10 patients with untreated chronic lymphatic leukemia. We plan to separate these B cell subpopulations and analyze their functional properties, and to perform chemical analyses of glycolipids of normal and leukemic B cells. Erythrocyte blood group antigens - We are performing chemical and immunological analyses of the erythrocytes of two new phenotypes of the blood group P system. One propositus appears to have a partial deficiency of the alpha-galactosyl transferase that synthesizes the Pkappa antigen, and another family appears to have a partial deficiency of the beta-galactosaminyl transferase that converts Pkappa to the P antigen.